Estudos citogenéticos, reprodutivos, moleculares e químicos como base auxiliar no melhoramento genético da erva-cidreira brasileira (Lippia alba), quimiótipo citral

Abstract

Bushy mat grass (Lippia alba) has great medicinal potential. However, selected genotypes are necessary, as there is a great chemical variation in their essential oil. Therefore, knowing its reproductive stability and how it reproduces are points of great importance. Modern technologies that contribute to the selection of plants for oil quality must also be implemented. Thus, the present research aimed to analyze meiotic behavior during the formation of pollen grains in Bushy mat grass genotypes, to investigate evidence of self-fertilization and barriers to their occurrence and to verify possibilities of applying DNA markers. ISSR (Inter Simple Sequence Repeats) in the selection of genotypes, for chemical quality of essential oil. To this end, genotypes of Bushy mat grass from the germplasm collection of the Department of Phytotechnics / Institute of Agronomy at UFRRJ were analyzed. In the first chapter, flower buds were collected and fixed in acetic acid and 70% ethanol until use. Anthers of the buds were removed and digested with pectinase / cellulase. Meiotic cells were stained with acetic carmine, and pollen grains with Alexander Triple Solution. The slides were observed under an optical microscope. The phases of meiosis, number of chromosomes, ploidy level and the meiotic indices (IM) and viability of pollen grains (VB) were analyzed. The genotypic determination coefficient and other important genetic parameters were also estimated from the IM and VB. The second chapter involved the collection of flower buds, after natural and artificial self-pollination, and after free pollination. The buds were softened with NaOH and stained with aniline blue. The slides were observed under fluorescence microscopy. The presence / absence of pollen tubes was observed in the stigma, style and ovarian cavity of the buds. The third chapter consisted of the analysis of 27 genotypes from the collection, from Minas Gerais and Rio de Janeiro, which had their oil extracted via hydrodistillation, from dry leaves and analyzed in gas chromatography (CG-DIC and CG-EM - with detector flame ionization and mass spectrometer). Genotypes also had their DNA extracted and analyzed via ISSR-type markers. Chemical and molecular diversity were estimated using UPGMA (Unweighted Pair Groups Method with Arithmetic Mean). The dendrograms were correlated to obtain the entanglement coefficient, whose objective was to verify how much the ISSR markers contribute in the selection of plants for essential oil quality. The results demonstrated meiosis without changes. The species is diploid with 2n = 2x = 30 chromosomes. IM (94.48%) and VB (94.32%) had greater genetic control (H2 = 91.50 and 76.77%, respectively). The genotypes did not present systems of genetic self-incompatibility, since pollen tubes were detected in their stigma, style and ovarian cavity. It is concluded that Bushy mat grass can be self-fertilized. Physical barriers to self-fertilization are likely. In chemical and molecular analysis, genotypes were grouped according to the chemical profile of essential oils. The entanglement coefficient was estimated at 0.24, indicating a high chemical and molecular correspondence. It was possible to apply ISSR markers for plant selection for essential oil quality in Bushy mat grass